Presently, gas turbine engine combustion chambers are difficult to design because of the different modes of operation of the gas turbine engine. The combustion chamber cannot provide for the optimum operating parameters at both idle power and full power, since the parameters for these extremities of operation are often contradictory. In practice, therefore, combustion chambers have been designed as a compromise between the desired ideal shape and volume required by the idle power requirements and the full power requirements.
A substantial problem in combustion chamber design is to provide the satisfactory richness of the fuel/oxidizer mixture. Experiments have been conducted toward reducing the flow of oxidizer (generally air) fed into the combustion chamber when the gas turbine engine is operating under idle conditions and to increase the oxidizer intake flow under full power conditions.
French Patent No. 2,065,688 describes a system which partially alleviates this oxidizer flow problem, but does not completely solve the problem for the desired full range of engine operation.